Since a motor-driven vehicle, i.e., an electric vehicle (EV) does not have an engine system, a power of the vehicle is controlled by a motor and an inverter. Particularly, the electric vehicle may cause an element temperature increase in an insulated gate bipolar transistor (IGBT) in the inside of an inverter during current/output use, and such a temperature increase in the IGBT may cause damage to power electric (PE) components. Here, the PE components mean a motor inverter using a power of a high-voltage battery and the like.
For this reason, an output is limited during current/output use in the inverter, thereby restraining a temperature of the IGBT from increasing. However, the output limitation of the inverter is unavoidable to have a rather negative aspect that output derating occurs, with a positive aspect that the temperature of the IGBT is restrained from increasing.
Specifically, when an electric vehicle is maintained in a hill holding state in an excessive uphill area over 30%, the output derating may not meet an output requested by a driver for hill holding maintenance, and may show a result of continuously reducing the output. For this reason, it is difficult for an electric vehicle to be maintained in a hill holding state, unlike a driver's intention, and a sudden torque/output drop which may occur in such a state may make the electric vehicle roll backward and thus may cause an unpredicted danger.
However, a brake cooperation control scheme of using oil pressure on the hill holding of an electric vehicle in an uphill area must take the reactivity of the oil pressure into consideration, and particularly, must solve the difficulty of having to overcome characteristics of the oil pressure, which is difficult in controlling a reaction speed and a request amount rather than a motor torque output speed.